The present invention relates to a method and an apparatus for injecting plastic into a multi-cavity mold with the aim of fabricating plastic parts.
The principle is known of using a mold having a plurality of cavities into which plastic is injected from a single injection cylinder. Ordinarily the dosing of the material is carried out in a central injection cylinder. The central injection cylinder contains a piston which delivers the material at a high pressure, for example, at more than 500 bars, towards the plurality of cavities. This injection operation occurs in a very short period of time, thus causing a large heat buildup effect due to the friction of the melted molten material against the walls of the runners between the plurality of cavities. Finally, these runners are filled with a plastic which, after solidification and removal from the mold, constitute a temporary spider-like formation interconnecting the molded parts. This temporary spider-like formation is then eliminated, representing a loss of material.
Additionally, when the mold is a reciprocal mold, that is, one into which movable pins are inserted at the moment of injection, the overhanging part on each pin is bent and shifted by the high-pressure flow of the material injected.